With advances in electronics, consumers have available to them a multitude of devices that were previously unavailable. Take, for instance, electronic navigation systems. Navigation generally refers to the art of determining a route on which to travel from one place to another, preferably as quickly and efficiently as possible. In around 3500 B.C., shipping vessels. navigated by remaining close to shore and relied on visual identification of landmarks or characteristics of the land they could observe visually. Therefore, these early sailors traveled by day and hesitated to venture beyond the sight of land. Some civilizations lit fires on land to aid in the navigation of vessels from point to point.
When early sailors did venture out of sight of land, the navigator determined a latitude position by observing the height of the sun during the day and the North Star at night. Additionally, some mariners plotted their course using major constellations, though this was not an exact science. Vessels followed the east/west movement of the sun or the track of the stars. However, the navigator had no way to accurately determine longitude and therefore, once out of sight of land, had no idea how far east or west he was. Estimates of position then were made based on the elapsed time of travel and direction of travel. Likewise, early land travelers often traveled great distances, navigating their way to remote locations and then back home based on the sun and other stars.
One of the earliest man-made navigation instruments is the compass. With early compasses, a navigator would rub an iron needle against a lodestone to magnetize the needle, place the needle on a piece of straw so that it would float, and place the straw in a vessel containing water. The magnetic charge on the needle would cause the straw to point in a north-south direction. Of course, this crude apparatus was inconsistent and susceptible to error. Also, like many of today's simple compasses, these early compasses would have pointed to magnetic north, which is several degrees off of the true North Pole.
One other invention used by early mariners was the lead line. Developed in the 13th Century, the lead line was used to measure the depth of water and the condition of the sea floor. The line was weighted and marked with a scale so as to be used to determine water depth. The weight at the bottom was also used to capture samples of the bottom. Thus, a method of navigation was to travel from one depth to another, and to make course determinations based on reaching certain depths and bottom conditions.
Early mariners also relied on the cross-staff aswell as the astrolabe to determine latitude by measure the angle of the sun and stars above the horizon. These are considered forerunners of the more accurate sextant, which was used well into the 20th century.
As mentioned above, early land based navigation also relied on celestial navigation techniques. However, land is infinitely more amenable to the marking of trains and roads and to the posting of signs. Thus, land and sea navigation techniques tended to diverge dramatically. While mariners moved toward radar and loran assisted navigation in the 20th. century, land travelers began to rely more heavily on following posted routes and navigating with maps and signs. However, both land and sea travelers faced shortcomings with their techniques until the Global Positioning System (GPS) was implemented commercially. The GPS is a worldwide, satellite-based navigation system that utilizes a constellation of 24 low-earth orbiting satellites (sometimes referred to by the acronym LEOS) on which an earth station can get a position fix.
More particularly, earth stations triangulate their positions based on timing signals received from a plurality of GPS satellites. A GPS receiver receives the timing signals from multiple satellites and, based on information such as satellite position and time of flight, uses this data to calculate a position of the receiver on the ground (or in the air).
The speed and accuracy of commercial GPS systems has led to a very high demand in many consumer markets. Although still an expensive option, GPS navigation systems are finding their way into boats, automobiles, golf carts and other vehicles in ever increasing numbers.